P2X purinergic receptors are ATP-activated ionotropic receptors having seven subtypes. The P2X7 receptor subtype (also known as the P2Z receptor) is a ligand-gated ion channel found on mast cells, peripheral macrophages, lymphocytes, erythrocytes, fibroblasts and epidermal langerhans cells. Activation of P2X7 receptor on such immune system cells results in release of interleukin-1beta. (Solle et al., J. Biol. Chemistry 276, 125-132, (2001)). The P2X7 receptor is also found on microglia, Schwann cells and astrocytes within the central nervous system (Donnelly-Roberts et al., Br. J. Pharmacol. 151, 571-579 (2007)).
Antagonists of P2X7 have been showned to block P2×7-mediated IL-1beta release and P2×7-mediated cation flux (Stokes et al., Br. J. Pharmacol. 149, 880-887 (2006)). Mice lacking the P2X7 receptor show a lack of inflammatory and neuropathic hypersensitivity to mechanical and thermal stimuli (Chessell et al., Pain 114, 386-396 (2005)). P2X7 is thus believed to have a role in inflammatory responses (Ferrari et al., J. Immunol. 176, 3877-3883 (2006)) and in the onset and persistence of chronic pain (Honore et al., J. Pharmacol. Ex. Ther. 319, 1376-1385 (2006b)). The P2X7 receptor has also been shown to mediate superoxide production in primary microglia, which is up-regulated in a transgenic mouse model of Alzheimer's disease (J. Biol. Chem. April 11, 278(15), 13309-17 (2003).
Modulators of the P2X7 receptor thus may have utility in the treatment of disease states such as rheumatoid arthritis, osteoarthritis, psoriasis, allergic dermatitis, asthma, chronic obstructive pulmonary disease, airways hyper-responsiveness, septic shock, glomerulonephritis, irritable bowel disease, diabetes and Crohn's disease. P2X7 modulators may also be useful for treatment of pain, including chronic pain, neuropathic pain, and pain associated inflammatory processes and degenerative conditions. P2X7 modulators may further be useful in the treatment of memory disorders such as Alzheimer's disease, and the enhancement of cognitive memory.
There is accordingly a need for compounds that act as modulators of P2X receptors, including antagonists of P2X7 receptor, as well as a need for methods of treating diseases, conditions and disorders mediated by P2X7 The present invention satisfies these needs as well as others.